My friend has a mountain bike that survived last years Queensland's floods (Australia, that is), but is all battered and bruised after not being ridden for a year. With my beginner's repair skills, I managed to make it almost roadworthy. The main problem now is the front brake lever: It will activate the brakes when pulled (and they work just fine) but the lever won't spring back into place when releasing it.

Any ideas as to why that might be? Is there some spring that has can be replaced or does the lever have to go altogether? I have applied some WD40 inside the lever as I noticed some rusty parts there, but it didn't do the trick.

Edit: I got some new cables and cable outers (cost me an arm and a leg here in Australia!), but it didn't do the trick. I dismantled the brake lever, only to see there is a spring inside the lever. (The spring resembles 2 circles of 5mm diameter with two 1mm vertical tips on either side. I presume that the tips serve to "hook" the lever & possible return it to position.)

This spring was rusty and fell apart when I tried to squeeze it. To conclude, since everything else is new, the issue is either: - This rusty spring that needs replacing, or - The 90o cable guide that was also rusty.

Yep, there's no spring inside the lever -- the spring on the brake itself "returns" everything. If it's not returning it's either due to too much friction or a brake spring that's broken or misadjusted. First guess is that the brake cable is rusted or perhaps crimped. (Be careful to keep lubricants off the brake pads and wheel rim.) (And, as stated, WD40 is a lousy lubricant. TriFlow is much better.)
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Daniel R HicksJan 10 '12 at 12:30

7 Answers
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My first guess is that the brake cable inside the brake cable housing is sticking. Some light oil on the cable could help. (WD40 is a solvent, do not use it on cabling or chains and do not use it where you want to maintain lubrication on parts. Look for some light oil like TriFlow, or whatever your LBS sells.) If the brake cable does not travel smoothly, I would suggest a new brake cable.

If you unhook the brake cable at the front brake arms, the arms should travel smoothly and you should feel some spring action that will resist squeezing. If the brake arms have no spring to them, that's a problem.

With the brake cable unhooked, the brake hand lever should move freely. If it doesn't then oil it. Light oil should penetrate any rust, and that might take 20 minutes of sitting before it works in.

Keeping the brakes in good condition is worthwhile and important. If you don't feel confident about how they feel, seek some help. Having a front wheel misbehave can be quite dangerous. Best of luck!

Completely agree with this answer (I'm voting up), but considering the bike is a flood survivor, I would recommend to completely replace the cables, as water must have got inside the cable casing and sure there is a lot of corrosion in there.
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JahazielJan 16 '12 at 4:08

SO won't let me upvote "WD40 is not a lubricant" and still upvote the rest.
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Mike SamuelSep 14 '12 at 16:30

I was having the same issue with my Cantilever brakes on my cyclocross bike (the brakes would stick and not return). My problem was not the brake lever or the springs on the brakes themselves. My brake pads were not engaging flat on the rim and created a lip on the brake pad. Park tool website has a great image at the end of the article for both Cantilever and Linear Pull (V-Brakes)

This little ridge was catching on the edge of the rim and not releasing the brake. I was able to take them off, use a razor blade and shave the ridge and adjusted the location to connect flat on the rim too, and my brakes no longer stick.

If this happens on the outside of the rim, then that ridge can eventually start chewing into the tire's sidewall.
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Mike SamuelSep 14 '12 at 16:32

I have had my pads too high as well - rubbing the tire raw, but don't get this type of ridge/lip when it rubs the tire, just when it is too low and is over the edge towards the spokes.
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Glenn GervaisSep 14 '12 at 18:01

I only have an anecdote. I had a front sidewall blowout after descending a steep narrow packed-earth track on 700x28s. When I looked for causes I found a worn line on the sidewall a little above where the rim would be, and a ridge such as you describe on one brake-pad. My best theory is that after a longish tour (Atlantic to Mediterranean through the Pyrenees with zigs and zags) with a maladjusted brake-pad where I was braking softly, I then did a white-knuckled descent putting more force on the brakes which did my tire in.
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Mike SamuelSep 14 '12 at 18:38

hey guys most of you seem to dismiss the fact that the spring in the break lever could be the problem but 9 times out of ten it is the spring and not the cable when i'm fixing breaks, don't assume any thing and give incorrect info to people please because that's the reason people get rid of perfectly fine bikes or bike parts, replace the spring man.

Like Daniel R Hicks mentioned, the brake lever is not spring loaded. The tension on the cable is provided by the spring on the brake. Check to see if the brake arms want to pull away from the wheel.

If they do, then you should just have to re-adjust the tension on the brake cable by loosening the nut which holds the cable, removing some slack on the cable, and re-tightening.

If they don't pull away, check the spring on the back of your brake arms. For v-brake or cantilever setup, there should be 3 little holes next to the brake bosses for the spring which provides tension to the brake arm. Make sure the spring on the back of the brakes is one of the holes on each side. You'll have to loosen the bolt holding them on the brake studs and put the spring end in one of the holes and re-tighten. Start with the center hole and if you need more tension, then use the lower hole. If this is setup right, both arms should try to push away from the wheel. After that, re-adjust the cable tension and everything should spring back. You may need to fine tune the cable tension using your barrel adjusters or by manually setting it with the bolt that holds the cable to the brake. You may also need to adjust the centering adjustment screw if one pad rubs the rim, but the other doesn't.

I'd have to agree with memnoch_proxy in that its more than likely your brake cable that has corroded. I'd replace both the inner and outer cable. The spring that exists inside of your brake lever is incredibly weak and its purpose is to return the lever to the original position when not connected to a bike. It will not be strong enough on its own to pull the brake cable back through.

If you are still having issues with the cable sticking then it will be to do with the spring on the brake caliper not on the lever.

makes sense what you say Rob. By "spring on the brake caliper" i take it that you mean this long & thing spring on either side of the brake arms (labeled "spring" on this diagram en.wikibooks.org/wiki/File:Brake_Drawing_3.jpg). Thanx in advance.
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Nikos JJan 19 '12 at 1:12

Yup, that's the chappy. Essentially its a bit of rigid wire that starts out straight as it runs along the arm of the brake caliper before being wound around the mounting bolt. One thing to do to see if it was this causing the problem is to unhook the brake cable from the 'cable bridge' (on your diagram) and see if each caliper arm moves freely and tries to spring out. If it doesn't then that's your problem.
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Rob ForrestJan 19 '12 at 16:37

You say "pull the cable": but if it were a spring in the lever doing the job, wouldn't it need to push the cable? I thought that the lever pulled the cable (to brake): to retract, can it be pushed? Or must it be pulled from the other end?
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ChrisWMar 5 '12 at 0:28

I am experiencing the same problem as the OP and I can confirm that the cause of his problem is NOT the cable but the spring that is inside of the mechanical disc brake itself. If you actually open up the caliper you will find the spring. While my spring is not broken or rusted it seems to be coming out of place during operation. There are two ends of the spring which slot into two holes. I'm assuming the spring is coming out of the holes and it would make sense given the symptoms of the problem. When I brake it starts to move the pad in but at a certain point you hear a snap and the brake loses pretty much all tension. The lever can be pulled all the way in without the pad moving at all or more braking force being applied past this critical point.

If I release the caliper from the brake cable entirely the problem is solved for a short while until I apply the brakes about 40 times at which point the issue resurfaces. Based on this it's safe to say that allowing the caliper to fully retract allows the inner spring to reseat itself into the two holes that hold it into place.

The only issue with this is....how am I going to find a spring to replace this one? I worked in a hardware store in the past and I know for a fact it will be next to impossible to get just the spring from the manufacturer for the exact part and finding a similar one in any retail store is slim to none.

I agree 100% with bike guy, the spring on the lever is there for a reason and that is to return the lever to is opening position. Replacing that spring is a little tricky but is cheaper than replacing the whole cable. Try it and leave a feedback to see who was right